Acrylonitrile Butadiene Styrene

Copolymer is a polymer formed from two or more chemically different monomers, copolymerized into a single chain. It is the basis of most modern plastics: it combines the properties of each monomer to produce materials with a superior stiffness/impact/chemical-resistance balance. ## Copolymer types - Random: monomers randomly distributed. e.g. EVA, random PP - Alternating: A-B-A-B-A-B... (rare in commercial plastics) - Block: A-A-A-B-B-B-A-A-A... e.g. SBS, block PP (impact) - Graft: main chain of A with B branches. e.g. ABS, HIPS - Statistical: similar to random but with a structural bias ## Key commercial examples - EVA (ethylene-vinyl-acetate): PE + acetate → flexible, transparent, sealable; soles, films - POM copolymer: formaldehyde + ethylene oxide; more hydrolysis-stable than homopolymer POM - Impact PP (PP-B): PP matrix + EPDM domains; low-temperature toughness - ABS: styrene + acrylonitrile + grafted butadiene; stiffness + impact + chemistry - PET-G: PET with CHDM as third monomer; amorphous, transparent, easy thermoforming - PVDF copolymer: with HFP; improved flexibility ## Advantages of copolymerization - Fine tuning of properties (Tg, transparency, impact, flow) - Better compatibility with additives / fillers - Better processability without sacrificing mechanics - Tailor-made design for a specific application ## Vs. homopolymer | | Homopolymer | Copolymer | |---|---|---| | Structural purity | High | Medium | | Crystallinity | Higher | Lower (typically) | | Stiffness | Higher | Lower (depends) | | Impact | Lower | Higher (with rubber domains) | | Clarity | Variable | Often improved |

Polymer is a macromolecule formed by the repeated covalent bonding of many small units called monomers. It is the molecular foundation of all plastics, rubbers, fibers and many biological materials (proteins, cellulose, DNA). ## Classification by origin - Natural: cellulose, starch, proteins, natural rubber, lignin - Synthetic: PE, PP, PVC, PS, PET, PA, PC, ABS… (most of the market) - Semi-synthetic: rayon, cellulose acetate, modified natural rubber derivatives ## Classification by architecture - Linear: straight chains (HDPE, PA 66, PS) - Branched: chains with branches (LDPE, ABS) - Crosslinked: PE-X, vulcanized rubber, thermosets - Dendritic: tree-like structures (specialty) ## Classification by thermal response - Thermoplastics: melt and reshape reversibly (PP, PE, PA, PC) - Thermosets: chemically cured, do not remelt (epoxy, phenolic) - Elastomers: flexible, recover shape after deformation (rubber, TPE) ## Classification by composition - Homopolymers: single monomer type (PE, PP-H) - Copolymers: two or more monomers (ABS = acrylonitrile + butadiene + styrene) - Blends: two polymers physically mixed (PC/ABS, PA/PPS) ## Key properties governed by structure - Molecular weight: stiffness and processability - Molecular-weight distribution: process window and toughness - Crystallinity: stiffness, opacity, shrinkage - Chain polarity: chemical resistance, adhesion, transparency

Thermoplastic is a polymer that softens and re-melts when heated above its melting or glass-transition temperature and solidifies again on cooling — with no permanent chemical reaction. This reversibility is what enables injection molding, extrusion and mechanical recycling of most plastics. ## Thermoplastic vs. thermoset - Thermoplastic: linear or branched chains without chemical crosslinks. Melts and can be remolded (PP, PE, ABS, PC, PA, PET, POM). - Thermoset: crosslinks chemically during cure (phenolic, epoxy, melamine resins). Cannot be remelted; reheating only degrades it. ## Classification of thermoplastics - Commodity: PP, PE-HD/LD, PS, PVC, PET → high volume, low cost - Engineering: ABS, PA (nylon), PC, POM, PMMA, PBT → improved mechanical properties - High-performance: PEEK, PPS, PSU, PEI, LCP → high service temperature, high cost - By structure: amorphous (PC, PS, ABS) vs. semi-crystalline (PP, PE, PA, POM) ## Processability Almost any thermoplastic can be injection-molded, extruded, thermoformed, blow-molded and roto-molded. Semi-crystalline grades require precise mold temperature to control crystallinity; amorphous grades tolerate wider windows. ## Recyclability and reuse Thermal reversibility allows scrap (regrind) to be ground and reprocessed up to 20 – 30 % mixed with virgin resin with no major property loss, depending on the polymer. Additives, cross-contamination with other resins, and accumulated thermal degradation limit the number of cycles.